The present invention relates to a new and improved construction of counter apparatus for counting substantially flat products, especially although not exclusively printed products, preferably moved in an imbricated formation or array along a conveying path or track.
Generally speaking, the counter apparatus of the present development is of the type comprising a feeler or sensor which can be elastically deflected in the conveying direction of the products by means of the leading ends of the products. This feeler coacts with an electric signal transmitter or the like which is responsive to the deflection of the feeler.
According to one such type of prior art construction of counter apparatus, as has been disclosed in German Patent Publication No. 2,446,184, and the cognate U.S. Pat. No. 4,091,269, granted May 23, 1978, the feeler is arranged between two loading disks which bear upon the product stream and possesses a nose member affixed to a spring-elastically deflectable support arm. In the rest position of the feeler, where the support arm bears against an inductive proximity switch, the nose member protrudes at a location beyond the circumference of the loading disks at a position which is located higher than the lowest point of such loading disks. The support arm is elastically deflected in the conveying direction of the products by means of the products which impact against the nose member by means of their leading edges. As soon as the nose member has been pushed back, by the products engaging thereat, to such an extent that it disappears between the loading disks this product is downwardly deflected by such loading disks. Consequently, the nose member releases from the product and the support arm can spring back into its rest position towards the proximity switch. The thus generated counting signal is delivered to a counter mechanism or counter.
With this prior art counter apparatus there is thus required a deflection of the products out of their conveying plane, in order to cause a release of the nose member and to render possible a return-positioning of the support arm. Apart from the thus required considerable expenditure in equipment this proposal is afflicted with the further drawback that such deflection movement, particularly when processing thin products, can result in damage thereto.
Additionally, there is known to the art from U.S. Pat. No. 3,219,829, granted Nov. 23, 1965, a counter apparatus wherein the feeler is pivotably arranged about an axis extending parallel to the plane of the products. This feeler is deflected against the force of a spring by the action of the leading edges of the products which inbound thereat. During such pivoting or rocking of the feeler a light beam of a light barrier or photoelectric arrangement is interrupted and thus generates a counting pulse which is inputted to a counter mechanism. With this prior art design what has been found to be particularly disadvantageous, apart from the unavoidable friction in the bearings of the feeler, is the relatively large inertia which can lead to faulty counts, particularly in the case of products arriving at a close mutual spacing and/or with the large conveying speeds which are encountered. Additionally, this counter apparatus is only suitable for products whose thickness does not fall below a minimum value. The deflection movement of the feeler which is caused, for instance, by one or two individual sheets, is not capable of positively interrupting the light beam of the light barrier and thereafter to again free such light beam.
In the counter apparatus disclosed in U.S. Pat. No. 4,139,765, granted Feb. 13, 1979 a feeler is continuously pressed from below, by the action of spring force, against the products which bear against one another in an imbricated product formation such that each product reposes upon the preceding product. Hence, the trailing edges of the products bear freely at the underside of the product stream which is scanned by the feeler. In order to ensure for a faultless contact of the feeler with the products it is necessary to provide above the product stream a contact or press roll located opposite the feeler.
The feeler is connected with a piezoelectric transducer which delivers a continuous signal in accordance with the contour of the product stream and the unevenness of the individual products. For counting the products there are evaluated those signals which are produced by the feeler ' following travel over the trailing edges of the products and the amplitude of which is greater than the remaining signals. These remaining signals must be filtered-out in order to obtain a correct count of the products.
Due to the deflection amplitude of the feeler which is limited in magnitude, this counter apparatus is not readily suitable for counting the products because of the steps which are formed by the leading edges of the products, since these steps are relatively high, particularly in the case of thick products, and possess a steep ascent. This counter apparatus therefore cannot be arranged at the top surface of an imbricated product stream where the leading edges of the products are located at the top, as such is normally the case when processing printed products.